The present invention relates to a solid-state imaging device, a method of manufacturing the same, and electronic equipment.
Electronic equipment such as a digital video camera and a digital still camera includes a solid-state imaging device. For example, as the solid-state imaging device, a CMOS (Complementary Metal Oxide Semiconductor) type image sensor and a CCD (Charge Coupled Device) type image sensor are included.
In the solid-state imaging device, a plurality of pixels is arranged on a surface of a substrate. In each pixel, a photoelectric conversion portion is provided. The photoelectric conversion portion is, for example, a photo diode, and creates a signal electric charge by receiving an incident light by a light sensing surface to perform the photoelectric conversion.
Among the solid-state imaging devices, in the CMOS type image sensor, the pixels are configured to include a pixel transistor in addition to the photoelectric conversion portion. The pixel transistor is configured to read the signal electric charge created in the photoelectric conversion portion and output the read signal electric charge to a signal line as an electric signal.
In the solid-state imaging device, generally, the photoelectric conversion portion receives the light that is incident from the front surface side on which a circuit element, a wiring or the like is provided on the substrate. In this case, since the circuit element, the wiring or the like shields or reflects the incident light, it is difficult to improve the sensitivity.
For this reason, there is proposed a “rear surface irradiation type” (e.g., see Japanese Unexamined Patent Application Publication Nos. 2003-31785, 2005-347707, 2005-35363, and 2005-353955) in which the photoelectric conversion portion receives the light that is incident from a rear surface side being an opposite side of a front surface on which the circuit element, the wiring or the like is provided in the substrate.
However, in order to suppress an occurrence of dark current due to an interface state of the semiconductor with the photoelectric conversion portion provided thereon, it is disclosed that the photoelectric conversion portion has a HAD (Hole Accumulation Diode) structure. In the HAD structure, by forming a positive electric charge accumulation (hole) accumulation area on the light sensing surface of an n-type of electric charge accumulation area, the occurrence of the dark current is suppressed.
In order to form the positive electric charge accumulation area in an interface portion of the photoelectric conversion portion, it is proposed that, by providing “a film having a negative fixed electric charge” on the light sensing surface of the n-type of electric charge accumulation area and peeling the same, the occurrence of dark current is suppressed. Herein, a high dielectric film having a high refractive index such as a hafnium oxide film (a HfO2 film) is used as a “film having a negative fixed electric charge” to suppress the occurrence of dark current, and the hafnium oxide film is used as an antireflection film to realize the high sensitivity (e.g., see Japanese Unexamined Patent Application Publication No. 2007-258684 (paragraphs 0163 to 0168) and Japanese Unexamined Patent Application Publication No. 2008-306154 (paragraph 0044 or the like)).